The applicant hereby incorporates by reference the disclosures of Robert P. Siegel et al., xe2x80x9cPredictive fuser misstrip avoidance system and method,xe2x80x9d U.S. Pat. No. 5,406,363, and Robert P. Siegel et al., xe2x80x9cPredictive decurler apparatus and method,xe2x80x9d U.S. Pat. No. 5,414,503, verbatim and with the same effect as though such disclosures were fully and completely set forth herein.
This disclosure relates generally to electric motors and, in particular, to a method for determining when an electric motor is acceptable.
Electric motors are commonly used in many devices and machines. For example, a copying machine uses a plurality of motors for various applications. One such application is for driving feed rollers for conveying a sheet of paper through a copying machine paper path for processing by the various copying functions.
Typically machines are returned to their manufacturer for service. When this occurs, it is common to remove the various motors from the machine. After removal, each motor is analyzed to determine if it is in acceptable condition to be re-used. The problem, therefore, is how to test an electric motor and determine its acceptability in an efficient manner.
Present methods of motor testing generally involve a xe2x80x9cone parameter at a timexe2x80x9d approach. Each parameter is measured and a determination is made to accept or reject the motor with respect to each parameter independently. For example, numerous motor testing methods are based on vibration analysis and current signature analysis. These methods are adequate when distinct defects are present, for example when looking for defects in a new production environment or in a field service troubleshooting situation where a problem has been reported. These methods are effective in detecting xe2x80x9chard failuresxe2x80x9d where the motor in question has departed in a clear and dramatic way from a known acceptable state.
The existing methods, however, do not address the case of a xe2x80x9csoft is failurexe2x80x9d where a motor is still performing its intended function, but has experienced a more subtle degree of degradation.
Therefore, there is a need for an improved method for determining when an electric motor is acceptable.
In one aspect of the invention, a testing apparatus is arranged for coupling to a motor. The testing apparatus determines when the motor is acceptable in accordance with a method. The method comprises: a) measuring a time required for the motor to reach a running speed in a steady state, thus forming a time-to-speed parameter; b) measuring a difference between an instantaneous speed and an average speed in the steady state, thus forming a speed variation parameter; c) measuring a maximum value of the motor current, thus forming a maximum current parameter; d) measuring a motor current in the steady state, thus forming a running current parameter; e) measuring a motor vibration energy in the steady state, thus forming a vibration energy parameter; and f) determining when the motor is acceptable based on the time-to-speed parameter, the speed variation parameter, the maximum current parameter, the running current parameter and the vibration energy parameter.
In another aspect of the invention, a testing apparatus is arranged for coupling to a motor. The testing apparatus determines when the motor is acceptable in accordance with a method. The method comprises: a) measuring a time required for the motor to reach a running speed in a steady state, thus forming a time-to-speed parameter; b) measuring a difference between an instantaneous speed and an average speed in the steady state, thus forming a speed variation parameter; c) measuring a maximum value of the motor current, thus forming a maximum current parameter; d) measuring a motor current in the steady state, thus forming a running current parameter; e) measuring a motor vibration energy in the steady state, thus forming a vibration energy parameter; f) measuring a motor current energy in the steady state, thus forming a current energy parameter; and g) determining when the motor is acceptable based on the time-to-speed parameter, the speed variation parameter, the maximum current parameter, the running current parameter, the vibration energy parameter and the current energy parameter.